Conventionally, a variety of drugs have been developed and clinically used for the cure and prevention of circulatory organ diseases. Among them, an antagonism against calcium particularly inhibits inflow of calcium ions into cells, which is caused by excitation of a cell membrane of cardiac muscle or vascular smooth muscle, controls contraction of such muscle and promotes vasodilation. A calcium antagonist, therefore, is useful for the cure and prevention of hypertension, angina pectoris, cerebral circulatory disturbances and the like.
As typical examples of such a calcium antagonism, furnarizine clinically applied as a cerebral circulation accelerator, cinnarizine clinically applied as an angiotelectasis agent, and the like are known. However, development of a new medicament, which has an antagonism against calcium with less side effect, has still been desired.
Accordingly, an object of the present invention is to provide a novel compound which possesses an excellent antagonism against calcium and is useful as a drug, and a drug containing this compound for circulatory organs.
Under such circumstances, the present inventors have carried out extensive studies and have found that a novel diphenylpiperazine derivative represented by general formula (1) as described hereinafter and its salts possess a strong antagonism against calcium compared with furnarizine or cinnarizine conventionally used, a less toxicity and a high safety and is widely applicable as a drug for circulatory organs.